Cathode-ray tube with combined clamping and shielding means



Feb. 8, 1966 SCHUBERT 3,234,423

CATHODE-RAY TUBE WITH COMBINED CLAMPING AND SHIELDING MEANS Filed March 2Q. 1961 I 5 5 I 3 )5 If 'l 7 lk A Jnvenfar:

United States Patent 3,234,423 CATHODE-RAY TUBE WITH COMBINED CLAMPING AND SHIELDING MEANS Rudolf Schubert, Nen-Ulm (Danube), Germany, assignor to Telefunken Aktiengesellschaft, Berlin, Germany Filed Mar. 20, 1961, Ser. No. 96,977 Claims priority, application Germany, Mar. 24, 1960,

18,111 4 Claims. (Cl. 31384) The present invention relates to the correction of distortions of the light spot in a cathode-ray tube, particularly where magnetic beam-deflection means are employed, which means include deflection coils mounted on the neck of the tube.

One prior-art means for magnetic deflection of an electron beam includes saddle-shaped deflection coils mounted on the neck of the tube. As viewed in a plane including the axis of the tube, the deflection field of such deflection coils follows the contour of a bell-shaped curve, ending substantially at the rear end of the deflection coils. However, when using toroidal deflection coils where the neck of the cathode-ray tube is surrounded by an annular yoke of ferromagnetic material on which the toroidal coils are wound, the contour of the field does not end at the rear end of the deflection coils but extends far behind the deflection coils. In some deflection systems, this interference field of the toroidal deflection coils is capable of counteracting the centering magnets located behind the deflection yoke and of causing other interference. In this case it has been the practice to abut the deflection coils on the rear side by a ferromagnetic ring, but this additional terminal ring is both relatively expensive and also considerably diminishes the amplitude of the deflection field.

In shallow cathode-ray tubes wherein the neck of the tube is relatively short so that the cathode-ray gun extends into the field of the deflection system, a distortion is frequently noticed which, during deflection of the beam, makes itself apparent in the form of distortion of the light spot on the picture screen of the cathode-ray tube. The present invention has as its primary object the elimination of this distortion.

The present improvement provides means for fastening the deflection yoke at its rear end to the neck of the tube, these means comprising a substantially cylindrical clamp of forrornagnetic material shaped and located so as to shield from the deflection field the electrode system, especially the electrostatic focussing electrodes located within the neck of the tube.

Additional objects and advantages of the present invention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawings in which the single figure shows a cathode-ray tube 1 with a deflection coil unit or yoke 2, the latter surrounding the neck and extending throughout part of its length. The deflection yoke is provided at its rear end with a cylindrical extension 3, which serves for fixing the yoke 2 by means of the clamp 4. It may be advantageous to provide slots in axial direction in this cylindrical extension 3 which allow the inner diameter to be varied by driving the screws 5.

A clamp 4 of ferromagnetic material is arranged on the cylindrical extension 3, which clamp secures the yoke 2 to the tube neck. The clamp is tightened by cooperating screws 5 preferably transfixing two bent-up lugs 6. The position of the clamp on the cylindrical extension 3 of the deflection yoke can be adjusted axially of the tube to an optimum shielding position with respect to the lens system 7 located within the neck of the tube. shown in the drawing is made relatively short, compared 7 The clamp m 3 ,234,423 Ice Patented Feb. 8, 1966 with the electrode system, but may, if desired be made to extend over the length of the whole system. Besides the width of the clamp, its shape and position over the electron lens system may be varied in such a Way as to achieve an optimum shielding effect.

The provision of this clamp of ferromagnetic material prevents the rearwardly-extending deflection-coil field from disturbing the lens system 7, thereby causing the cathode-ray beam not to undergo pre-deflection while still within the lens.

It will be understood that the above description of the present invention is susceptible to various modifications, changes, and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

What is claimed is:

1. A cathode-ray tube arrangement comprising, in combinat-ion:

(a) a cathode-ray tube having a neck;

(b) an electrostatic focussing system arranged within said tube neck;

(c) a magnetic deflection unit arranged exteriorly of said tube and having a cylindrical extension which is coextensive with a portion of the length of said neck and encompasses the same generally in the region of said electrostatic focussing system within said tube neck; and

(d) means for both attaching said magnetic deflection unit to said tube and shielding said electrostatic focussing system from the magnetic field of said magnetic deflection unit, said means being constituted by a clamp made of ferromagnetic material which firmly encompasses said extension of said magnetic deflection unit thereby to clamp the same to said neck of the said tube, said clamp having the shape of a cylinder which is coaxial with respect to said neck of said tube and also closely surrounds the same in said region of said electrostatic focussing system, in consequence of which said ferromagnetic clamp serves simultaneously to fasten said magnetic deflection unit to said cathode-ray tube as well as to shield said electrostatic focussing ssytem within said tube neck from the magnetic field of said magnetic deflection unit, thereby to prevent distortions of the light spot in the cathode-ray tube which would otherwise be caused by the effect of the magnetic field on said electrostatic focussing system.

2. The arrangement defined in claim 1 wherein said extension is yieldable.

3. The arrangement defined in claim 2 wherein the yieldability of said extension is obtained by the fact that said extension is provided with axially extending slots which allow the diameter of said extension to be varied.

4. The arrangement defined in claim 1 wherein the axial dimension of said extension is greater than that of said clamp, in consequence of which said clamp is displaceable on and with respect to said extension in the direction of the axis of the tube neck.

References Cited by the Examiner UNITED STATES PATENTS 2,717,324 9/1955 Hall 31394 2,830,213 4/1958 Leeds 313-846 2,889,477 6/1959 King et al 313-84.6 2,907,914 10/1959 Brownell 3158 2,922,908 1/1960 Heller 31376 X ROBERT SEGAL, Acting Primary Examiner.

RALPH G. NILSON, DAVID J. GALVIN, GEORGE N. VJESTBY, Examiners. 

1. A CATHODE-RAY TUBE ARRANGEMENT COMPRISING, IN COMBINATION: (A) A CATHODE-RAY TUBE HAVING A NECK; (B) AN ELECTROSTATIC FOCUSSING SYSTEM ARRANGED WITHIN SAID TUBE NECK; (C) A MAGNETIC DEFLECTION UNIT ARRANGED EXTERIORLY OF SAID TUBE AND HAVING A CYLINDRICAL EXTENSION WHICH IS COEXTENSIVE WITH A PORTION OF THE LENGTH OF SAID NECK AND ENCOMPASSES THE SAME GENERALLY IN THE REGION OF SAID ELECTROSTATIC FOCUSSING SYSTEM WITHIN SAID TUBE NECK; AND (D) MEANS FOR BOTH ATTACHING SAID MAGNETIC DEFLECTION UNIT TO SAID TUBE AND SHIELDING SAID ELECTROSTATIC FOCUSSING SYSTEM FROM THE MAGNETIC FIELD OF SAID MAGNETIC DEFLECTION UNIT, SAID MEANS BEING CONSTITUTED BY A CLAMP MADE OF FERROMAGNETIC MATERIAL WHICH FIRMLY ENCOMPASSES SAID EXTENSION OF SAID MAGNETIC DEFLECTION UNIT THEREBY TO CLAMP THE SAME TO SAID NECK TO THE SAID TUBE, SAID CLAMP HAVING THE SHAPE OF A CYLINDER WHICH IS COAXIAL WITH RESPECT TO SAID NECK OF SAID TUBE AND ALSO CLOSELY SURROUNDS THE SAME IN SAID REGION OF SAID ELECTROSTATIC FOCUSSING SYSTEM, IN CONSEQUENCE OF WHICH SAID FERROMAGNETIC CLAMP SERVES SIMULTANEOUSLY TO FASTEN SAID MAGNETIC DEFLECTION UNIT TO SAID CATHODE-RAY TUBE AS WELL AS TO SHIELD SAID ELECTROSTATIC FOCUSSING SYSTEM WITHIN SAID TUBE NECK FROM THE MAGNETIC FIELD OF SAID MAGNETIC DEFLECTION UNIT, THEREBY TO PREVENT DISTORTIONS OF THE LIGHT SPOT IN THE CATHODE-RAY TUBE WHICH WOULD OTHERWISE BE CAUSED BY THE EFFECT OF THE MAGNETIC FIELD ON SAID ELECTROSTATIC FOCUSSING SYSTEM. 